Luke11CNC Build Log ,I'm so naïve

[jcb121]

Luke, What are you using for the bed of your machine?

For mine I was thinking 20mm Aluminium but I'm swaying more towards 10mm or 15mm due to Cost of water cutting, postage and materials.

Unlike mine you have a frame though....

[JAZZCNC]

Luke, What are you using for the bed of your machine?

For mine I was thinking 20mm Aluminium but I'm swaying more towards 10mm or 15mm due to Cost of water cutting

Depending on the frame support centre's on your bed then I wouldn't go less than 15mm.!
If you look at the link below you will see my bed made from 16mm strips with 10mm gaps spaced at 45mm centres and the support beams are spaced approx 400mm centres.
Overall it works great and soon will be upgraded again which hopefully will make it just that bit better. The bed (which is adjustable height) will be removed and a stainless steel box fitted underneath so mild flood coolant can be used and will filter and catch the chips which will be dumped into a collection bin.

If doing again I'd lessen the support beam centres to 300mm and use 20mm strips, that said the 16mm works great just feel 20mm would give it that bit more meat allowing for a longer lasting bed after it as been surfaced a few times. With 16mm the distance from the clamping boltd head to surface determines the amount of usable bed surfacing.
Thou unless some major coding cockup goes on it will be years before that's a problem.!!. . .that said it only took me 2wks before I'd drilled a nice 6 hole ballnut pattern into.
http://www.mycncuk.com/forums/showth...-machine/page8

Edit: The reason I used strips was 2 fold.
1: cost of plate Ali too much wonga
2: Didn't like the thought if a major cock up happened then the whole plate was screwed up, with strips I just replace any that get damaged if I have a brain fart when coding or machine goes on rampage.! It also made slots for T-nuts easy.
( By the way I use the 10mm T-nuts for KJN profile because the drop between the slots and when twisted self lock which means I dont have to have an access point at either end of the bed like you do with STD T-nuts on a mill making clamping anywhere on the bed easy.

[luke11cnc]

Jes for now just a sheet of MDF Untill after Christmas but then I will be fitting this

http://www.aluminiumwarehouse.co.uk/...duct_info.html

with a 10mm gap for t nuts

James

[luke11cnc]

this will cost me £160.00+vat

9@4000
1@2000

James

[Jonathan]

I was about to post saying see what Jazz has done for his bed, but luckily refreshed the page...
I'm intending to do the same with some sort of tray underneath so I can use coolant efficiently.

Jazz, it sounds like you don't put anything between the part you are cutting through and the bed, just let the cutter mark the bed and surface it occasionally? It must take a long time to cut the surface considering it's aluminium. I surface the MDF at 8m/min but you're not going to go that fast on aluminium!

At the moment my bed is made from MDF and pine, it's a grid of 3x1 PAR wood with 18mm MDF on the top and 9mm underneath. That's clamped on top of two steel rails (box section), which mount to the frame for adjustable height. I've only changed the height once in the past 3 months...
It's like that because before I made the steel frame for my machine the X-axis rails mounted directly on to the bed, so the bed needed to be rigid.

Jes for now just a sheet of MDF Untill after Christmas but then I will be fitting this
http://www.aluminiumwarehouse.co.uk/p16210/Aluminium_Flat_Bar_-_Imperial_Sizes_(6082T6)_1_in_x_⁵/₈_in/product_info.html
with a 10mm gap for t nuts

That gives you a roughly 71% aluminium (29% air...) bed, compared to 78% for Jazz's 35mm(?) strips. Not much less to be fair, but more frequent clamping slots, so only slightly weaker but as Jazz says he'd prefer them to be thicker anyway. Probably not much in it, but something to think about.

this will cost me £160.00+vat

9@4000
1@2000

That's 840mm wide which is 24 strips and you can get 3 strips per 4m length, so surely that's only 8@4000 (still £160). Or were you thinking of using the other bits for the perpendicular pieces underneath?

[luke11cnc]

so would you recommend using 3/4x7/8 19.05x15.88mm then Jonathan ??

switches and cable ordered Jonathan

James

[luke11cnc]

Looking at the price list Jonathan I may go with 20x20mm so I have 5 or 6 mill worth of surface trimming so it should last me quite a while

what do you think ??

James

[Jonathan]

It makes sense to use thicker, so yes 20mm. However I'd be inclined to use wider than 20mm strips (only 67% with 20mm and 10mm gap) for additional strength. It's less work to 40x20 compared to 20x20. If you went to maybe 40mm wide you can get two bolts side by side in each strip which should be stronger - less twisting? Not sure...

[luke11cnc]

good point Jonathan

James

[JAZZCNC]

Jonathan: Yes I do always put something between the bed and part. Depending on the job at hand.?
If it's a non critical job that the top surface be exactly parallel to bed or thru drilling then I just use any thing to hand that resonably flat IE MDF off cuts.
If it's more important it's parallel to bed but doesn't need to be exactly 100% perfect and doesn't have any drilling involved then I use a 1mm thin ridged card board I bring from work that doesn't compress.
If it has to be exactly 100% perfect and must cut thru or involve drilling then I have several sized 15mm HDPE slabs that I clamp to the bed then surface. MDF is no good for this because the minute you cut the top layer it turns into a shape shifter and no matter what folks think MDF aint flat or parallel thickness.
To be honest 60% of the time the card board is used 30% MDF 10% HDPE.

That said regards MDF.? I've just been given an MDF type paper product sheet that is resin impregnated. It's used to make the cubicles in swimming baths and shower area's. It doesn't swell no matter how wet, even when submersed under water. This I know to be true because this sheet was outside for 8mths.
I've just used a piece as a spoil board and it machines like plastic and surfaces with a perfect finish because of the resin.
Really it's the perfect product for a long lasting disposable bed topper.! . . thou I do understand it's very expensive.

James: (Or anybody who's interested)

Here's how I did it. (It was a bit tedious but worth it) . . . . Material 1"1/2 x 5/8 (38.1x15.88mm)

Using a 90Deg spot drill in the spindle find the centre of bed and scribe boxsection. Then mark the first strip exactly in the centre then bolt down exactly in the centre of the bed lining up with scribed mark.
Then using a 8mm spacer working out both sides bolt down each strip to bed. Then using a 8mm twin flute end mill create a climbing milling toolpath to cut the 10mm slots in 2 depth pass's, didn't want to use a 10mm endmill as it would have been cutting on both sides and required much less DOC taking longer and leaving a worse finish. . . .(Yes I know the 8mm cuts on both edges but only on the way up not down.)
Reason I did it this way was because I have some machine clamps that use 45mm centres. They could have been just butted with a 10mm spacer but there are other bennifits to machining the slots for me(see below). . . . Plus the strips arn't exactly straight.!!

Doing it this way I know exactly that all my slots are exactly parallel to the X axis. Across the very top (Yaxis) and down the outer edge (X axis) as a strip that bolts on top of bed and acts as referance edge, which again is machined parallel and square. I've made some 45mm wide aluminium strips (various lengths from offcuts) that have a 3mm notch down the centre with the edges machined parallel that fits tight into the slots and can be used as positionable reference edges anywhere on the bed ( WHY.? Because I like to cut in differant parts of the bed to save wear on the ballscrews from always cutting in the same spot.)

James I would go with the 3/4 or better still 1" the little extre expense will be worth it.